Replacing RO/DI Filters

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balto777

New member
I have a 5 stage RO/DI system from The Filter Guys. I bought it about 6 months ago and my color changing resin has changed from completly black to completly dark orange, and I assume it needs to be changed soon. Because I live in an area that has high TDS and uses chloramine, I assumed my DI resin would be used faster than normal, even though I got their chloramine buster filters.

My question is: Will chloraine or any of its deriviatives show up on a TDS meter. Also, will Ammonia show up as TDS. The reason I ask is because I have a separate TDS meter to use to determine whether my filters need replacing, but I heard that the first substances released when the DI filter is full is chlorine and ammonia. If this is the case, I need to know whether the TDS meter is enough to check for this.

As of now, my TDS readings are:
Tap Water: ~480 TDS
RO Water: ~27 TDS
RO/DI Water: ~0 TDS

Thanks in advance to everyone for their help.
 

rbursek

In Memoriam
RO membraines last much longer then the DI, Jim has told me at TFG's that the DI will ussually give good water even after it has changed color, mine from him does for me. If I remember right Randy H-F stated that yes amonia will be the first thing given up by the DI. It should be dedected by your TDS meter. Jim also said do not have to change the DI until you to 2 TDS on the DI out. It is more important to stay current on you sediment and carbon block filters, the CB is what filters out the chlorine.
 

balto777

New member
I thought I read somewhere that ammonia and chlorine are not dissolved solids and therefore could not be registered on a TDS meter?
 

Randy Holmes-Farley

Reef Chemist
Premium Member
The TDS will rise from 0 ppm to 1 ppm when things first start to get out in important concentrations, so that is a fine way to gauge. I discuss it here:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria
http://reefkeeping.com/issues/2005-05/rhf/index.htm

from it:

If you are evaluating an existing RO membrane and can collect water from the tap and after the RO membrane, the conductivity (in mS/cm or ppm TDS) should drop by a factor of more than 10 across it (to as much as 100), relative to the tap’s water. If the drop is less than a factor of 10, it is not working properly, and may have holes in it.

Monitor the DI resins by measuring the effluent’s conductivity, either with an inline meter (set to its most sensitive level), or by measuring the effluent manually. If you are using a TDS or conductivity meter, then the measured value should drop to near zero, or maybe 0-1 ppm TDS or 0-1 mS/cm. Higher values indicate that something is not functioning properly, or that the DI resin is becoming saturated and needs replacement. That does not necessarily mean, however, that 2 ppm TDS water is not OK to use. But beware that the flow of impurities and the conductivity may begin to rise fairly sharply when the resin becomes saturated. Do not agonize over 1 ppm versus zero ppm. While pure water has a TDS well below 1 ppm, uncertainties from carbon dioxide in the air (which gets into the water and ionizes to provide some conductivity; about 0.7 mS/cm for saturation with normal levels of CO2, possibly higher indoors) and the conductivity/TDS meter itself may yield results of 1 or 2 ppm even from totally pure water by not being exactly zeroed properly. Also note that the first impurities to leave the DI resin as it becomes saturated may be things that you are particularly concerned with (such as ammonia if your water supply uses chloramine or silica if there is a lot in the source water).
 

Boomer

Bomb Technician (EOD)
Premium Member
but I heard that the first substances released when the DI filter is full is chlorine and ammonia.

Well, it is not chlorine but chloride which is not a concern. Chloride is a major ion in seawater. So, it is the chloride ion that may use it up. However, most of the chloride ion will get removed by the RO. It is the carbon block filter that converts the chlorine to chloride. Much of the Ammonia will pass through, get converted to ammonium, which has a charge and can deplete the DI.


Ammonium or Chloride will show up as TDS. However, the meter going from say 0 ppm TDS to 2 or 3 ppm for example does not mean it is these two. It may be them or a combination of them or other ions.

One of the big concenrs for the DI is CO2. Measuring the the TDS of the input RO and output RO and the ALk will allow one to calculate how much of the DI is being depleted by CO2.

To calculate the effects of CO2 on a DI, measure the pH and Alk of the RO output water. Then from this calculator detemine the CO2 in ppm.

http://www.fishfriend.com/aquarium_co2_calculator.html

Divide the CO2 RO output by the sum of the RO output CO2 + the RO output TDS

For example, if you have 4 ppm TDS and 4 ppm CO2 in your RO water, 4/8 or 50% of your anion DI resin is being depleted by just CO2.



This wil go into much greater detail

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria
http://reefkeeping.com/issues/2005-05/rhf/index.htm
 

AZDesertRat

In Memoriam
The answers are yes and yes, they will show up with a TDS meter. The bad thing is if chlorine shows up in your effeluent your membrane is toast. What you are probably also passing on are nitrates, phosphates and silicates all of which are weakly ionized and will pass through spent DI resin readily.
Don't waste money on color changing resins or chloramine filters.
Use a single 0.5 or 0.6 micron Matrix Chlorine Guzzler type carbon block preceded by a high quality absolute rated prefilter like a 0.5 or 0.5 micron which will protect that expensive carbon block and that is all you need. This is proven technology.
If you have a tap water TDS of 480 and you are only getting a RO TDS of 27 you are not working very efficiently and its no wonder DI resin does not last, thats only 94% rejection. You should be seeing a RO TDS of no more than 18 or 19 tops and it should really be in the range of 4 to 10 or less.
My tap water TDS is 835 and my RO only TDS is only 5 to 6. Not all membranes are the same, neither are DI resins, prefilters or carbon blocks. With a TDS of 480 you want better performance than that or DIcosts will eat you up in a hurry.

Use your handheld TDS meter on a regular basis to monitor your system. It will NOT tell you when you need to change the prefilter and carbon blocks for the most part s they are designed to protect the RO membrane which is the workhorse. It will tell you the condition of the membrane and DI resin though and is much more accurate and reliable than color changing resin or inline meters.
 

balto777

New member
I am sure I have the Dow FilmTec 75 GPD membrane, which should have a 98% rejection rate. What reasons are there that I am only getting 94%. I have not noticed it slowly decreasing, it has always been that amount since I started testing.
 

AZDesertRat

In Memoriam
Membranes are not guaranteed as to either GPD or water quality performance, they can be +/- 15% off the shelf. Spectrapure is the only company that provides guarantees on their membranes.
 

Boomer

Bomb Technician (EOD)
Premium Member
Aaron

I would call Jim at TFG he will take care of you hands down. It could be that some of the water is going around the RO, it is no uncommon in the RO industry. If it is bad unit it is a guaranteed it will get replaced.

Rat

There is no such thing as a Filmtec 75 GPD RO being off +/- 15 % off, off the shelf if running required line pressure. Show me where that data comes from when using normal line pressure. You are stating or coming across that that the rejection rate can be only 83 % on a 98 % membrane or 113 %. No such thing as 113 %.
 

Thefilterguys

.Registered Member
<a href=showthread.php?s=&postid=12199189#post12199189 target=_blank>Originally posted</a> by balto777
Always love reading the Reef Chemistry Forum for all the information you guys share.

Thanks alot! :)

please contact me for correct information if you have low pressure your rejection rate can indeed be lower then 98% but no one seems to touch on that. Your current RO tds of 27 without CO2 will only make about 180 gallons of water out of a full sized cartridge.

Jim
 

Thefilterguys

.Registered Member
<a href=showthread.php?s=&postid=12204015#post12204015 target=_blank>Originally posted</a> by AZDesertRat
Membranes are not guaranteed as to either GPD or water quality performance, they can be +/- 15% off the shelf. Spectrapure is the only company that provides guarantees on their membranes.

Mr Rat I suggest you go read your company Spectrapure website on membranes as your information couldn't be more wrong you don't seem to know your production rate from you rejection rate.

Jim
 

loudell

New member
<a href=showthread.php?s=&postid=12204015#post12204015 target=_blank>Originally posted</a> by AZDesertRat
Spectrapure is the only company that provides guarantees on their membranes.

I am puzzled as to what this statement means. Please clarify.
 

Boomer

Bomb Technician (EOD)
Premium Member
Hay me to Lou ;)

Rat

You are the one that posted +/- 15 % not me. You are the one requried to show it...dude, as it is your claim, to include the Spectrapure remarks.
 

Thefilterguys

.Registered Member
<a href=showthread.php?s=&postid=12204015#post12204015 target=_blank>Originally posted</a> by AZDesertRat
Membranes are not guaranteed as to either GPD or water quality performance, they can be +/- 15% off the shelf. Spectrapure is the only company that provides guarantees on their membranes.


Let me see if I can spell it out for you Rat since you are the poster boy for Spectrapure. If your conditions don't meet these requirements all bets are off and let me tell you most hobbists don't meet these conditions. I think what they say is read the fine print or between the lines.

FROM SPECTRAPURE WEB PAGE

Guaranteed minimum 98% rejection or better
Membranes produce rated GPD ± 10% at 60 psi
250 ppm softened tapwater, 77°F (25°C),


Minimum Rejection = 96%
The membranes produce the rated GPD ± 20% at 60 psi
250 ppm softened tapwater, 77°F (25°C),
 
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balto777

New member
Looks like I opened up a can of worms!

Anyway, Thefilterguys, if my 27 tds water yields about 180 gallons of water, then that confirms that it is time to order another DI filter cartridge because I have made about that much so far. (I only have a 20 gallon tank) If it came across differently, I am not complaining about your RO/DI units, in fact I am completely satisfied. (In fact I have already ordered a replacement filter set from you guys, should be here early next week) I thought water pressure can effect the rejection rate, and to tell you the truth, I am happy with 94%, since I am just using regular water pressure without a pump.

Again, I thank you guys for answering my original question, whether I could use a TDS meter to detect when my filter is in danger of releasing Amonium and/or Chloride back into the final water.
 

Thefilterguys

.Registered Member
Aaron your fine don't worry about the worms we'll go fishing. Someone on the board ask me to take a look at the thread and see if I could help.

Lower water pressure will reduce the rejection rate no matter who's membrane you have. Chloramine filtration takes long carbon contact time and the higher the filter quality the better, that is why we came up with special filters. We highly recommend going no longer then six months between carbon filter changes. If your municipal water supplier is using high levels of chloramine you may not even get six months before you see filter slowdown. We believe two stages of carbon is extremely important to get the contact time and breakdown. Much of the byproduct will be filtered by the membrane and the balance removed by the DI resin. Zero tds by whatever meter you use is your goal. Color changing resin is only a heads up to pay attention for exhaustion so trust the reading on your meter as resin can change color and still produce zero tds. We specialize in chloramine and have it in our own municipal water system and it is deadly to fish.

Jim
 
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AZDesertRat

In Memoriam
No, Spectrapure guarantees their Select membranes to produce better than 98% rejection rate at 77 degrees and 60 psi. They also go a step further and guarantee them to produce at least the rated GPD at 77 degrees and 60 psi. I am not aware of anyone else offering this guarantee.

I find it funny when someone has been in the business a whopping two years and they now become the expert.
 
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